Quite numerous: Galway-Mayo. Probably same as Deasy, q.v. which makes the Irish Déiseach,(native of Decies, Waterford). The presence of these "exiles" in Connacht in 17 & 18 cent may signify transplantation. MIF.

Deasy:

numerous: W Cork etc. Ir. Déiseach, native of the Decies, Waterford. This territory is a tribal designation pre-dating surnames. See also Deacy. MIF.